This invention relates to railroad cars and more particularly to articulated railroad cars for transporting wheeled vehicular trailers. The present invention finds use in transporting truck trailers in "piggyback" fashion to destinations close to the ultimate delivery destination of the trailer contents. At that point, the truck trailers are lifted off the railroad cars and hitched to tractors for ultimate delivery of the goods.
It is desirable to be able to transport more than one truck trailer on each car in order to establish economical freight rates which will induce truckers and trucking companies to use railroad facilities rather than highways. To this end, the railroad cars may be articulated, i.e., constructed of two or more platforms or decks connected at a joint which allows relative movement between the decks. Not only must the decks be able to pivot or shift relative to one another in a horizontal plane to negotiate curves, but also the connecting joint should accommodate decks at different relative heights such as when one deck is loaded with a trailer and the adjacent deck is not.
Railroad cars are customarily supported by wheel trucks at their forward and rearward ends. In many of the large railroad car constructions, each wheel truck includes a supporting frame and two wheels mounted on each of two parallel axles, commonly referred to as a double axle wheel truck. In an articulated car, it is desirable that each deck be supported at its forward and rearward end so that the decks can be separated for repair and maintenance, and are self supporting. To help reduce costs, it would be desirable to use single axle wheel trucks which include only two wheels and one axle rather than the double axle wheel trucks described above. One of the problems which arises with single axle wheel trucks is their inability to withstand the forces imposed upon them and maintain the car on the track. This is especially true when the cars are skewed and are being pushed, for in that mode forces on the rail cars tend to cause the articulated car decks to jackknife and the car to derail.
Accordingly, it would be desirable to provide an articulated railroad car which includes a plurality of articuated decks each supported by a single axle wheel truck at its forward and rearward end and which can pivot or shift relative to one another in both horizontal and vertical directions. In addition, it would be desirable that the connection between the decks tend to correct skewing therebetween when the car is being pushed thereby minimizing the likelihood that the decks will jackknife.